Long-term impact of reduced tillage on water and pesticide flow in a drained context

Abstract

Influence of more than 20 years (1988-2010) of reduced tillage (RT) practices on water and pesticide balances and dynamics is analyzed and compared to results from a conventional tillage plot (CT). The field study soils are described as silty clay stagnic luvisol, developed on a low permeable schist layer. A drainage network was set up according to French criteria (0.9 m deep, 10 m space) to avoid soil winter waterlogging. Climate is temperate oceanic and drainage generally occurs from November to March. Data were analyzed at yearly, weekly (pesticides) and hourly (water) time steps. Over the long term, cumulated drainage decreases significantly on RT (3999 mm) compared to CT (5100 mm). This differentiation becomes significant from 1999, 10 years after plowing was stopped. Strikingly, hourly drainage peak flows are higher under RT, especially during the second period (2000-2010), associated with low or no base flow. These results suggest a strong influence of the macropore network under RT practice. In particular, drainage peaks are higher at the beginning of the drainage season (mid-October to December). Consistently, pesticides applied in late autumn, which are the most quantified on this site, are often significantly more exported under RT. For atrazine, applied in spring, fluxes are linked to cumulative flow and are de facto higher under CT. For others pesticides, losses appear to be heterogeneous, with generally low or null export rates for spring application. Generally speaking, higher concentrations are measured on RT plot and explain observed exportation rate differences. Finally, there is no clear evidence of correlation between pesticide losses and long-term impacts of RT on hydrodynamics, pointing the importance of studying the short-term effect of tillage on water and especially solute flow.

Tillage Intensity Effects on Soil Structure Indicators—A US Meta-Analysis

“…Reducing tillage intensity can help mitigate soil erosion and generally improves biological and physical soil health. If coupled with cropping system diversification NT can increase SOM, AS, biological activity, connectivity of soil pores and permeability [3,12,15,[20][21][22]. However, those responses are not consistent as reflected in other studies that have reported soil structure degradation under NT.…”

Lime movement through highly weathered soil profiles

“…Reduced-and no-tillage have been widely adopted to reduce soil erosion and are currently used worldwide on approximately 150 million hectares (Kassam et al 2015). No-tillage has also been incorporated into several conservation practices, adapted to increase crop diversification, and shown to improve soil health and provide both environmental and economic benefits (Kassam et al 2015, Dairon et al 2017. It has also been identified (FAO (2016)) as an important soil management component of conservation agriculture, but NT is not without its challenges and improvements are needed to expand its adoption and capture its societal benefits.…”

How does tillage intensity affect chemical soil health indicators? A United States meta‐analysis

“…Conservation and reduced tillage practices were initiated in the United States to reduce soil erosion following the 1930s Dust Bowl, but adoption is still below 40% in most states (CTIC, 2019). An important driver for soil health is that in addition to reducing soil erosion, decreased tillage intensity can also improve physical and biological soil properties (Dairon, Dutertre, Tournebize, Marks‐Perreau, & Carluer, 2017; Nunes, Karlen, Veum, Moorman, & Cambardella, 2020). However, effects of tillage intensity on chemical soil health indicators (i.e., soil pH and nutrients) within the profile are still uncertain because of potential accumulation at or near the soil surface and depletion within subsurface layers (Deubel et al., 2011; Noack et al., 2014; Nunes et al., 2019).…”